Structural element having low heat conductivity



JanQZ, 1945. I Q, DEAN 4 2,366,60IL

STRUCTURAL ELEMEfiT 'najvme LOW HEAT CONDUGTIVITY Filed May 29, 1940 Amman/V555 Java/afar eza/mw 5. BMW

I Patented Jan; 2, 1945 STRUCTURAL ELEMENT HAVING LOW HEAT CONDUCTIVITY Reginald S. Dean, Salt Lake City, Utah, assignor to Chicago Development Company, Chicago, 11]., a corporation of Illinois Application May 29, 1940, Serial No. 337,823

1 Claim. (01. 62-1) This invention relates to elements of construction made from alloys having low heat conductivity. It relates especiall to such elements of construction made from alloys having low heat conductivity combined with other mechanical properties which make them suitable for the construction of mechanisms wherein it is desirable to maintain a temperature gradient between different parts of the mechanism and having a mini-v mum flow of heat along this gradient. It relates especially to elements of construction for the construction of mechanisms where reduction of vibration is desirable in connection with the property of low heat conductivity. It will be obvious that such engineering requirements are met with in the construction of refrigerating systems and the like where the compressor unit which evolves heat must be maintained in a closed circuit with the cooling coils which are at a low temperature. It will be clear that if these cooling coils are connected to the compressor unit by means of copper tubing or other high conductive material considerable energy will be lost due to heat flow through this. tubing from the compressor unit to the cooling coils. This loss is greatly reduced by the application of my invention.

be obvious to those familiar with the automotive and refrigerating industry. In one preferred form of my invention, I use an alloy composed of 82 parts of manganese and 17 parts of copper. 1 have disclosed, in prior copending' applications, methods for-the manufacture and heattreatment of this alloy to obtain improvedmechanical properties and high vibration damping "capacity. I have found that this alloy has exceptionally low heat conductivity and is, therefore, well suited to the practice of my invention. I have found that this particular alloy has less than 5% of the heat conductivity of. copper. I have found that'other alloys high in manganese may be used, particularly those containing manganese and copper with from 50 to '90% of The elements of construction of my invention have an additional advantage in the construc-' tion of freezing units for refrigerator systems in that they have an exceptionally high vibration damping capacity. Consequently, the vibrations which are an unavoidable part ofthe compressor system will not 'be transmitted to the cooling coils. The application of my invention is not limited to mechanical refrigerating systems, but is also of value in the so-called gas refrigerators or in any other system where a temperature gradient must be maintained between one part of the system and another, and where the heat flow through the constructional material of such a system must be reduced to a minimum.

In addition to the use of my invention in concopper does not manganese. Such alloys have from 5% to 8% of the heat conductivity of copper. I have also found that nickel may be substituted for the copper either in whole or in part without greatly increasing the heat conductivity. The addition of nickel increases the mechanical properties. The mechanical properties as well as the electrical resistance of alloys of the ternary system copper, nickel and manganese as well as, the

binary systemscopper manganese and copper nickel have been disclosed in my copending applications. While there is no accurate parallelism in these alloys between heat conductivity and electrical conductivity, I havefound, in' the,

ordinary case, that any of these alloys having an electrical resistance greater than 100 microhms per centimeter cubed may be successfully used for the practice of my invention. It should be emphasized, however, that the preferred'alloy, namely an alloy of 82 manganese and 17 /2% have as high an electrical resistance as a number of other alloys of the systems referred to which are less satisfactory for the mechanical type. The cooling coils are con- .nection with refrigerating systems, it will,

practice of my invention:

A specific example of the vention involves a refrigerating unit of the usual structed of copper and the compressor of steel. In accordance with one aspect of my invention, between the compressor unit and the cooling coils, as illustrated in the accompanying drawing, there is inserted a length of two feet, in each end of the coil, of an alloy containing 82 manganese, 17 copper, such alloy having been prepared in the form of seamless tubing by the usual processes. Before being inserted in the system, this tubing is heated to a'temperature of 900 degrees C. and quenched in oil. In the operation of such a refrigeration system, in comparison application of my inreduced and a saving of using a central wire containing approximately 80% manganese and 20% nickel, this wire having been prepared by the usual fabrication proccesses and heat treated by slow cooling from about 1000 degrees C. The ceramic insulator is attached to the wire in as nearly identical fashion with a standard spark plug as possible and the two spark plugs placed in service in a test engine. The useful life of the plug having a manganese alloy electrode is nearly twice that ofthe other plug.

It will be understood that the above examples are merely illustrative of the application of my invention which encompasses elements of construction made from alloys containing high percentages of manganese, in which elements a large temperature gradient is maintained with a minimum of heat flow. It will be seen, therefore, that I may construct structural members which may transmit power or-may merely act as a combintially made up of one atlon support and heat insulator in places where normal low heat conductivity material is lacking in necessary physical or electrical properties. While, for the most are found in alloys of 50% to 90% manganese. balance copper and/or nickel, the alloy may lie somewhat outside of this specific range. For example, small proportions cf other alloying elements may be added to modify the physical properties. An alloy as high as 97% manganese may at times be employed, containing, for example, in addition to the manganese, 2% of copper and 1% of nickel.

.For a further understanding of the maimer of producing the alloys employable in' accordance with the present invention, reference may be made to Patents Nos. 2,202,012; 2,230,236; 2,234,428 and 2,259,459. g

What I claim as new and desire to protect by Letters Patent of the United States is:

A refrigerating mechanism in which th;

cooling tubes are separated from the remainde 'of the mechanism by means of hollow members made from an alloy containing at least 50% manganese, the remainder of the alloy being substanor both of the elements of nickel.

REGINALD S.DEAN.

the group copper and part, the properties desired 

